1. Field of the Invention
This invention relates to a tractor having a vehicle frame with a pair of right and left elongate frame members spaced from each other and extending in a longitudinal direction and interconnected in intermediate positions by a cross member, an engine supported by the elongate frame members in a front region of the vehicle frame, a rear axle unit connected to rear axle connecting members fixed to the elongate frame members in a rear region of the vehicle frame, and a drive transmitting mechanism for transmitting drive from the engine to the rear axle unit, a front loader and/or a backhoe being attachable to a front and a rear of the tractor as supported by the vehicle frame.
2. Description of the Related Art
A tractor with a front loader and a backhoe attachable thereto as noted above, i.e. a so-called tractor-front loader-backhoe (TLB), is subjected to overloads such as compressive, tensile, twisting and bending forces acting on a vehicle frame when running with the backhoe attached to the rear end or during an excavating operation with the backhoe. Thus, the tractor must have a highly strong chassis to withstand such heavy loads. TLBs with such strong chassis are known from U.S. Pat. Nos. 4,087,009 and 4,661,036, for example.
Further, it is common practice to connect a reinforcing frame unit to a rear region of a vehicle frame to which a backhoe is attached, whereby the entire vehicle frame becomes strong enough to withstand overloads occurring when running with the backhoe attached to the rear end or during an excavating operation with the backhoe. Tractors with such reinforcing frames are known from U.S. Pat. Nos. 5,000,269 and 5,248,237, for example. U.S. Pat. No. 6,056,502 discloses a technique of connecting a front end of a reinforcing frame to a forward region of a vehicle frame by a flexible structure.
In any case, in connecting a reinforcing frame unit to a rear region of a vehicle frame, according to conventional practice, reinforcing frame connections are formed on the vehicle frame adjacent connections of a rear axle unit fixed to the vehicle frame.
That is, in the prior art noted above, a structure elastically deformable relatively freely is not provided between the rear axle connections and the reinforcing frame connections that are formed adjacent each other on the vehicle frame. Consequently, overloads occurring when running with a backhoe attached to the rear end or during an excavating operation with the backhoe are transmitted straight to the axle unit. It is therefore necessary for the casing of the rear axle unit also to have sufficient strength to withstand such overloads. As a result, the rear axle unit tends to be large and expensive to manufacture. It is difficult to attach a backhoe to a small tractor, in particular, for which lightweight and low cost are desired features.